This invention relates to a method of platinizing and heat treating tantalum and more particularly tantalum plugs to be used as electrodes in the detection of faults in reaction vessel protective linings.
It is a common practice to use protective layers of glass enamel as an anti-corrosive lining on the inside of reaction vessels which contain corrosive liquids. In such vessels, a fault in the protective lining can result in serious corrosion of the vessel, and if such a fault remains undetected for some time, the vessel may become unusable and irreparable. In some cases, the contents of the vessel may even become contaminated. Thus, it can be seen that vessels of this type must be continuously monitored against damage to the protective lining.
U.S. Pat. No. 3,858,114, which is incorporated herein by reference, discloses a method for detecting faults in reaction vessel linings. The method described in this patent involves disposing a platinum electrode in a conductive medium in the vessel and measuring any current flowing from the electrode to the iron or steel wall of the reaction vessel. At locations where damage has occurred to the lining, the current flow increases accordingly. The intensity of the current delivered by the so formed Pt-Fe cell indicates the degree of damage to the protective layer. The platinum metal used as an electrode in U.S. Pat. No. 3,858,114 is very expensive. It would therefore be worthwhile, if possible, to plate a tantalum core with platinum and use it as an electrode. Such an electrode would have a platinum surface and tantalum core and would be less expensive than conventionally platinum plated electrodes. Tantalum has been chosen as a core material because it is corrosion resistant and should the platinum layer of the electrode break down, the tantalum will not adversely affect the contents of the vessel. It has been found in practice, however, that conventionally plated platinum layers on tantalum wear out rather quickly, particularly when the contents of the vessel contain an abrasive material such as slurry.